1. Technical Field
The present invention relates in general to car bon nanotubes and, in particular, to an improve and system and method for broad-area synthesis of aligned and densely-packed carbon nanotubes.
2. Description of the Related Art
Carbon nanotubes (CNT) have excellent structural, thermal and electrical properties, especially along their length. These properties, however, have not been even closely realized on the macro scale. Such a bulk material could be stronger than steel and more conductive than copper but lighter than aluminum. CNT grown on a substrate by chemical vapor deposition (CVD) is a promising synthesis technique since the CNT self-align perpendicular to the substrate resulting in a “forest” of CNT of fairly uniform height. Unfortunately, the packing density per area of the CNT is limited to about 10% for known CVD methods. Since the out-of-plane properties of the bulk CNT product should scale with packing density, it is desirable to pack as many CNT together per area as possible.
Small patches of CNT forests densified by liquid-induced collapse have been demonstrated by a few research groups with an area of 1 square centimeter or less. In particular, D. N. Futaba, et al (Nature Materials, December 2006) physically detached and removed the CNT forest prior to densification; whereas, N. Nicholas et al (unpublished) chemically detached the CNT forest but left it in place on the substrate. In both cases, the coverage area of the densified product was much smaller than the initial undensifed forest area. This was achieved with a single growth step and a single liquid-induced densification step. Although these solutions are viable, they have limited practical application and an improved solution would be desirable.